HCG
Last updated: June 2026
HCG 500 IU Twice Weekly: How Many Syringe Units to Draw
500 IU twice weekly is one of the most common HCG schedules used alongside testosterone therapy and for fertility support. This guide shows the exact arithmetic that turns that 500 IU dose into a syringe-unit mark, once you know how the vial was reconstituted.
HCG 500 IU: how many units on the syringe depends on your reconstitution
There is no single answer to HCG 500 IU, how many units on the syringe, because IU is a dose and a syringe unit is a volume mark. The number of units you draw for 500 IU changes entirely with how much bacteriostatic water you mixed into the vial. The same 500 IU can read as 10 units, 20 units, 25 units, or 50 units depending on the final concentration.
Two facts have to be settled before any unit number is meaningful: the vial strength (commonly 5,000 IU or 10,000 IU) and the volume of water you added during reconstitution. Together those give a concentration in IU per mL, and the concentration is what converts a dose into a draw volume.
This page assumes a standard U-100 insulin syringe, where 100 units equals 1 mL. If you are new to that scale, see HCG IU to syringe units explained first.
The math: dose IU divided by concentration, then convert to units
The conversion is two short steps. First find the concentration the vial reached after you added water. Then divide your dose by that concentration to get a volume in mL, and convert the mL to syringe units.
- Concentration (IU/mL) = total vial IU ÷ water added in mL
- Draw volume (mL) = dose IU ÷ concentration
- Syringe units (U-100) = draw volume in mL × 100
A useful shortcut for U-100 syringes: units = (dose IU ÷ concentration) × 100. Because 500 IU is fixed here, the only thing that moves the unit number is the concentration you created when you reconstituted the vial.
Example
Vial: 5,000 IU. Water added: 1 mL. Concentration: 5,000 ÷ 1 = 5,000 IU/mL. Dose: 500 IU. Volume: 500 ÷ 5,000 = 0.10 mL. Units: 0.10 × 100 = 10 units.
If you would rather not do this by hand each time, enter your exact vial strength, water volume and 500 IU dose into the HCG dosage calculator and read the unit mark directly.
500 IU units chart for a 5,000 IU vial
The 5,000 IU vial is a common size dispensed for HCG alongside testosterone therapy. The table below shows the syringe units for a 500 IU dose at four typical water volumes. Every row is the same 500 IU dose; only the water changes.
| Water added | Concentration | Draw volume | Units (U-100) |
|---|---|---|---|
| 1 mL | 5,000 IU/mL | 0.10 mL | 10 units |
| 2 mL | 2,500 IU/mL | 0.20 mL | 20 units |
| 2.5 mL | 2,000 IU/mL | 0.25 mL | 25 units |
| 5 mL | 1,000 IU/mL | 0.50 mL | 50 units |
Example
Vial: 5,000 IU. Water added: 2 mL. Concentration: 5,000 ÷ 2 = 2,500 IU/mL. Dose: 500 IU. Volume: 500 ÷ 2,500 = 0.20 mL = 20 units.
More water means a weaker concentration and a larger, easier-to-read unit number for the same dose. This is the same principle covered in why water amount changes syringe units.
500 IU units chart for a 10,000 IU vial
If your vial is 10,000 IU, the same 500 IU dose lands at a smaller unit mark for any given water volume, because the powder is twice as concentrated. The table below shows the result at common reconstitution volumes.
| Water added | Concentration | Draw volume | Units (U-100) |
|---|---|---|---|
| 2 mL | 5,000 IU/mL | 0.10 mL | 10 units |
| 5 mL | 2,000 IU/mL | 0.25 mL | 25 units |
| 10 mL | 1,000 IU/mL | 0.50 mL | 50 units |
Notice that a 10,000 IU vial with 2 mL of water gives the same 10-unit draw as a 5,000 IU vial with 1 mL of water, because both reach 5,000 IU/mL. The unit mark follows the concentration, not the vial size. The difference between the two vial sizes is covered in HCG 5,000 IU vs 10,000 IU vials.
What 500 IU twice weekly means for the week and the vial
500 IU twice weekly is 1,000 IU per week total. Splitting the weekly amount into two injections keeps each dose small and the volume easy to draw. The injections are usually spaced out across the week, for example one dose every three to four days, though the exact schedule is set by your prescriber.
The schedule also tells you how long a vial lasts. A 5,000 IU vial holds ten 500 IU doses, which at two doses per week is five weeks of supply, if the reconstituted vial is still within its usable window. A 10,000 IU vial holds twenty 500 IU doses.
Example
5,000 IU vial ÷ 500 IU per dose = 10 doses. At 2 doses per week: 10 ÷ 2 = 5 weeks of doses, subject to the vial’s storage limits after mixing.
Reconstituted HCG has a limited refrigerated shelf life set on the product label, so a vial that contains five weeks of doses on paper may need discarding before all doses are used. See HCG storage and expiry for the storage window after mixing, and always follow the discard date on your specific product label.
Common mistakes when drawing 500 IU
The most frequent error is copying another person’s unit number. Someone drawing 25 units for 500 IU mixed their vial differently from someone drawing 10 units. The dose is identical; the concentration is not. Always run your own vial strength and water volume through the math.
- Assuming a fixed unit number. 500 IU is not a fixed number of units. It is 10 units at 5,000 IU/mL but 50 units at 1,000 IU/mL.
- Mixing up vial strength and concentration. A 5,000 IU vial is not 5,000 IU/mL until you know the water volume. Strength is the total in the vial; concentration is the amount per mL after mixing.
- Forgetting to recompute after re-mixing. If you reconstitute a new vial with a different amount of water, the unit mark for 500 IU changes. Recalculate every time.
The principle that the same unit mark can mean different doses is covered in why 10 units does not always mean the same dose. HCG dosing should be set and supervised by a prescribing clinician; this page is a measurement tool, not a dosing recommendation.
FAQs
How many units is 500 IU of HCG on an insulin syringe?
It depends on concentration. On a U-100 syringe, 500 IU is 10 units if the vial is at 5,000 IU/mL, 20 units at 2,500 IU/mL, 25 units at 2,000 IU/mL, and 50 units at 1,000 IU/mL. Find your concentration first, then units = (500 ÷ concentration) × 100.
I have a 5,000 IU vial and added 1 mL of water. What do I draw for 500 IU?
That vial is at 5,000 IU/mL. 500 ÷ 5,000 = 0.10 mL, which is 10 units on a U-100 insulin syringe.
Is 500 IU twice weekly the same as 1,000 IU once a week?
The weekly total is the same, 1,000 IU. Splitting it into two doses changes the timing and keeps each injection small. Whether to split a dose is a clinical decision for your prescriber, not a maths question.
How long does a 5,000 IU vial last at 500 IU twice weekly?
On dose count, a 5,000 IU vial holds ten 500 IU doses, which is five weeks at two doses per week. In practice the reconstituted vial may need discarding sooner based on the post-mixing storage window printed on the product label.
Why does the same 500 IU dose give a different unit number for my friend?
Because they reconstituted their vial with a different amount of water, so their concentration differs. Never copy another person's unit mark. Match your own vial strength and water volume to get the correct draw.
Read next
Hcg Reconstitution GuideSources
- Novarel (chorionic gonadotropin) for injection, for intramuscular use — prescribing information. DailyMed, U.S. National Library of Medicine. dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ac6918ff-9dc3-40d9-8619-54b26e4bdfc8.
- Coviello AD, Matsumoto AM, Bremner WJ, et al. Low-dose human chorionic gonadotropin maintains intratesticular testosterone in normal men with testosterone-induced gonadotropin suppression. J Clin Endocrinol Metab. 2005;90(5):2595-2602. academic.oup.com/jcem/article/90/5/2595/2836735.
- Hsieh TC, Pastuszak AW, Hwang K, Lipshultz LI. Concomitant intramuscular human chorionic gonadotropin preserves spermatogenesis in men undergoing testosterone replacement therapy. J Urol. 2013;189(2):647-650. pubmed.ncbi.nlm.nih.gov/23260550.
- McBride JA, Carson CC, Coward RM. Diagnosis and management of testosterone deficiency. Asian J Androl. 2015;17(2):177-186. pmc.ncbi.nlm.nih.gov/articles/PMC4650468.
This guide is for general educational purposes only and does not constitute medical advice. Always follow your prescriber's specific instructions.